A semiconductor bridge (“SCB”) die device has typically been configured to include a pair of conductive lands connected together by a narrower conductive bridge segment. The bridge segment may be formed from doped or undoped silicon, either alone or having an upper layer of a metal such as tungsten or titanium disposed thereover. The lands may also comprise silicon, oftentimes covered with a layer of, e.g., aluminum. Other configurations of the die exist in the art. The conductive lands are commonly connected to a source of electrical energy (e.g., an active power source or a stored charge device such as a capacitor). For use as an explosive initiator or igniter, the bridge segment is typically placed in close physical contact with an explosive charge (e.g., a pyrotechnic material charge). In various embodiments of these devices, an electrical current passing through the bridge causes plasma to form from the electrically activated bridge material, wherein the plasma subsequently initiates or ignites the explosive charge. The explosive charge may be connected by, e.g., a shock tube, to a detonator device that detonates upon initiation or ignition of the explosive charge by the SCB device.
In addition, the SCB die is typically connected to a header device. The header may comprise ceramic, glass, metal or other suitable material. The bottom surface of the SCB die may connect to the top surface of the header by, e.g., a soldered connection or epoxy. Besides this physical connection of the SCB die to the header, an electrical connection from the electrically conductive SCB die to pins (typically two pins) on the header also exists. The header pins are then connected to the electrical power source.
Prior art SCB devices typically utilize bondwires (e.g., 5 mils in diameter) to make an electrical connection from the top surface of the die (i.e., from the metallized conductive lands on the die) to the pins or other suitable contact areas on the header. However, issues regarding the use of bondwires may include bondwire cutoff smearing aluminum across the glass seal which surrounds the pin to be wirebonded, sub-optimal bondwire configuration for relatively small geometry applications, minimum powder load requirements to assure the bondwires do not touch the output cup, added header cost due to the unique features required for wirebonding, electrostatic discharge issues, and with respect to high volume applications the cost of capital equipment required for wirebonding at high speed.
For these and other reasons, it is known to eliminate the bondwires and use some type of electrically conductive surface connection between the bottom surface of the SCB die and the top surface of the header. Such a surface mounted SCB die enables igniters with relatively smaller charges to be readily manufactured since the header can be made with a smaller diameter and the minimum powder bed above the die can be reduced, as there are no bondwires that might contact the output cup. However, these and other common known approaches for connecting the SCB die to the header without bondwires (e.g., submounts and wraparound metallization) are relatively limited in their applicability, for example, in that they require relatively tightly controlled header dimensions. Also, these methods are of relatively high cost and not easily manufacturable.
Vertical holes have been manufactured but fabricating die with metal on the insides of the holes has proven problematic. What is needed is a tapered or “slope-sided” SCB die and method for making such a die wherein the resulting die is relatively more easily solderable to the header through use of a surface mounting technique without the use of bondwires, the connection between the die and the header being relatively more reliable, the dimensional requirements of the header are relaxed to a certain degree, and the manufacture of the SCB die and header, along with the soldering of the die to the header, are all of relatively lower cost.